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Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
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Home | Pregnancy Timeline | News Alerts |News Archive Jan 9, 2015

Cold temperatures may encourage "unhealthy" white fat cells to change into "healthy" brown fat.




Exposure to cold 'switches' white fat to brown fat

New research has uncovered a part of our metabolism with great flexibility. Thirty percent of cells that appear to be white fat rapidly turned into brown fat cells after being mildly stressed with cold temperature.

The roles that white fat and brown fat play in metabolism are well documented, but new research in the January 2015 issue of the FASEB Journal of the Federation of American Societies for Experimental Biology, presents a new realization — each type of fat may change into the other depending on temperature. It seems that cold temperatures may encourage "unhealthy" white fat to change into "healthy" brown fat.

Brown fat is abundant in newborn human babies where its primary function is to generate body heat so newborns will not shiver. While white adipocytes (fat cells) contain a single lipid (fat) droplet, brown adipocytes contain numerous smaller droplets and a much higher number of (iron-containing) mitochondria within each - thus appearing brown. Brown fat also contains more capillaries than white fat as it needs a greater amount of oxygen than most tissues.

"Fat cells can adopt a range of metabolic phenotypes, depending on physiological conditions and location in the body. Our long-term goal is to harness this cellular and metabolic flexibility for the treatment of metabolic disorders linked to dysfunctional fat, such as type 2 diabetes."

James G. Granneman PhD, Center for Integrative Metabolic and Endocrine Research, Wayne State University School of Medicine, Detroit, Michigan.

Scientists tagged two specific cell populations for their experiments. The undifferentiated progenitor (or originating) cells and differentiated adipocytes (fat cells) in mice before exposing them to mild cold stress. Then researchers traced whether these cells became brown adipocytes in other fatty tissues within the mice.

Results showed that in existing classic brown fat tissue the tagged progenitor (originating) cells divided and became new brown fat. This required neural activation and a specific growth factor receptor on the cell. In contrast, the vast majority of brown fat cells that appeared in white fat tissue were simply tagged with a marker from mature fat cells.

The study found that about 30 percent of cells that appear to be white adipocytes rapidly turned into brown adipocyte cells following cold stress.

"If you want to rev up your metabolism, don't throw out your winter coat just yet," adds Gerald Weissmann, M.D., Editor-in-Chief of the FASEB Journal. "We still need know if this holds true in humans. What's more, the important part of this research is that one type of fat can change to another, and that cold triggers cellular mechanisms that lead to the formation of more brown fat. The 'switch' that controls what type of fat is created may be a promising drug target for a variety of obesity-related illnesses."

This work investigated how cold stress induces the appearance of brown adipocytes (BAs) in brown and white adipose tissues (WATs) of adult mice. In interscapular brown adipose tissue (iBAT), cold exposure increased proliferation of endothelial cells and interstitial cells expressing platelet-derived growth factor receptor, α polypeptide (PDGFRα) by 3- to 4-fold. Surprisingly, brown adipogenesis and angiogenesis were largely restricted to the dorsal edge of iBAT. Although cold stress did not increase proliferation in inguinal white adipose tissue (ingWAT), the percentage of BAs, defined as multilocular adipocytes that express uncoupling protein 1, rose from undetectable to 30% of total adipocytes. To trace the origins of cold-induced BAs, we genetically tagged PDGFRα+ cells and adipocytes prior to cold exposure, using Pdgfra-Cre recombinase estrogen receptor T2 fusion protein (CreERT2) and adiponectin-CreERT2, respectively. In iBAT, cold stress triggered the proliferation and differentiation of PDGFRα+ cells into BAs. In contrast, all newly observed BAs in ingWAT (5207 out of 5207) were derived from unilocular adipocytes tagged by adiponectin-CreERT2-mediated recombination. Surgical denervation of iBAT reduced cold-induced brown adipogenesis by >85%, whereas infusion of norepinephrine (NE) mimicked the effects of cold in warm-adapted mice. NE-induced de novo brown adipogenesis in iBAT was eliminated in mice lacking β1-adrenergic receptors. These observations identify a novel tissue niche for brown adipogenesis in iBAT and further define depot-specific mechanisms of BA recruitment.—Lee, Y.-H., Petkova, A. P., Konkar, A. A., Granneman, J. G. Cellular origins of cold-induced brown adipocytes in adult mice.

Authors: Yun-Hee Lee, Anelia P. Petkova, Anish A. Konkar, and James G. Granneman Cellular origins of cold-induced brown adipocytes in adult mice. FASEB J. January 2015 29:286-299; doi:10.1096/fj.14-263038 ;http://www. fasebj. org/ content/ 29/ 1/ 286. abstract

The FASEB Journal is published by the Federation of the American Societies for Experimental Biology (FASEB). It is the world's most cited biology journal according to the Institute for Scientific Information and has been recognized by the Special Libraries Association as one of the top 100 most influential biomedical journals of the past century.

FASEB is composed of 27 societies with more than 120,000 members, making it the largest coalition of biomedical research associations in the United States. Our mission is to advance health and welfare by promoting progress and education in biological and biomedical sciences through service to our member societies and collaborative advocacy.

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